Night vision devices gather existing ambient light (starlight, moonlight or infra-red light) through a collection lens unit. The collected light passes through an image intensifier typically based on a photocathode tube. In such photocathode tube, an input light signal causes emission of electrons from the photocathode which propagate to a luminescent screen producing a light output. Some types of image intensifiers utilize a micro-channel plate (MCP) which works as an electron amplifier and is placed directly behind the photocathode. The MCP consists of a large number of short parallel glass tubes. When the electrons pass through these short tubes, thousands more electrons are released.
FIG. 1 illustrates schematically the conventional approach for night vision devices. As shown, an imager, such as CMOS or CCD, is equipped with an image intensifier, e.g. of the kind utilizing an MCP, where the photocathode and luminescent screen structure of the image intensifier are kept at high potential difference (i.e. high operating voltage). Thus, the image intensifier provides an intensified light signal input to an electronic device including the CMOS/CCD imager. There, the light signal is converted into an electrical signal and transmitted to the CMOS/CCD read out circuit.